JPH0476802B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an ultra-low pressure pneumatic tire, and is used for tires for wheels running on rough terrain, such as buggies. (Prior Technology) As an ultra-low pressure (inner pressure around 0.15 kg/cm ² ) pneumatic tire for buggy vehicles for sports, leisure, and competition that drive mainly on muddy, grassy, snowy, and sandy areas, JP-A-Sho. There is a technique disclosed in Japanese Patent No. 60-33104 (Conventional Example 1). (Problems to be Solved by the Invention) In the conventional example 1, the blocks on the tread are arranged to form a herringbone pattern in the circumferential direction, and although the maneuverability during cornering can be improved, this type of tire is Since the rigidity of the block itself is low and the pressure is extremely low, there was a problem that the block would sink during straight running, resulting in insufficient straight running performance and traction performance. In addition, because the density (number) of blocks arranged in large numbers on the tread is too large, when driving on muddy or snowy roads, the problem arises that mud and snow become clogged, significantly reducing traction and maneuverability. The present invention improves straight running performance by distributing the force applied to the blocks to the left and right by arranging the center blocks located on the tire equator in a square shape and alternating left and right in a staggered manner. Another object is to reduce the number of blocks as much as possible by arranging two side blocks and one side block on both the left and right sides of the central block, thereby preventing clogging with mud or the like. (Means for Solving the Problems) In the present invention, a tread 2 located in the center is connected to both side walls 4 through a shoulder 3, and a block 11 having a trapezoidal cross section is placed on the tread 2 including the shoulder 3. The following technical measures have been taken to achieve the above-mentioned objective in ultra-low pressure pneumatic tires arranged in large numbers in That is, in the present invention, the blocks 11 include a center block 12 arranged along the tire equator LL, side blocks 13 arranged on both left and right outer sides of the center block 12, and side blocks 13 arranged on both left and right outer sides of the side blocks 13. The central block 12 is formed into a U-shape in plan view through the bent portions, and is arranged in a left-right staggered manner with the bent portions overlapped on the tire equator L-L. The side blocks 13 are arranged in a staggered manner, with two on the left and one on the left. The shoulder blocks 14 have a herringbone pattern in which the side blocks 13 are obliquely arranged in the anti-tire rotation direction 15A, and the shoulder blocks 14 have a length in the tire axial direction in the two left and right side blocks 13. In the small short block 14, in the left and right side blocks 13, there is a long block 14 with a large length in the tire axial direction.
Each of the blocks 11 is characterized in that the kick surface portion 9 has a large rising angle with respect to the tire outer surface, and the opposite kick surface portion 10 has a small rising angle. (Function) According to the present invention, the tire 1 is arranged as indicated by the arrow 15 in FIG.
When rotated in the direction, the kick surface 9 of each block 11
This causes the vehicle to move through mud, sand, snow, etc. on the road surface. When this running is straight, the bending part of the center block 12 which is shaped like a bow will touch the ground in advance, but the center blocks 12 are arranged in a staggered pattern with left and right alternating, and with this center block 12 as a reference, the left and right Since two side blocks 13 and one side block 13 are distributed on both sides to form a herringbone pattern, blocks 12, 13
It distributes the force applied to the left and right sides to ensure straight travel, and the total number of blocks is reduced to prevent clogging with mud, etc. Further, excessive deformation of the shoulder 3 is suppressed by the shoulder block 14, which consists of a long block and a short block, so the number of blocks can be reduced by dividing the side blocks 13 into two on the left and one on the left. To prevent the total tractive force from becoming small even if it is reduced. In addition, since the rising angle of the kick surface portion 9 of the block 11 is larger than that of the counter kick surface portion 10,
The surface of the road surface is wide and the adhesion of mud, etc. is reduced. (Example) In FIGS. 1 and 2, 1 is a pneumatic tire, in which a tread 2 located in the center is connected to both sidewalls 4 through both shoulders 3, and a bead core 6 is connected to the bead portion 5. Each bead core 6 is connected by a carcass ply 7 wound thereon. This tire 1 is made of rubber or other elastic material, a bead portion 5 is fitted onto a rim 8, and the internal pressure is set to an extremely low pressure of about 0.15 kg/cm ² by a valve means (not shown). As shown in FIG. 3, on the tread 2 including the shoulder 3, a large number of blocks 11 each having a trapezoidal cross section with a kick surface portion 9 and a counter kick surface portion 10 are arranged in the horizontal direction and arranged in a herringbone pattern in the circumferential direction. There is. The blocks 11 include a center block 12 arranged on the tire equator LL, side blocks 13 arranged on both left and right outer sides of the center block 12, and shoulder blocks 14 arranged on both left and right outer sides of the side blocks 13. It consists of The grounding portion 12A of the center block 12 has a U-shape in plan view, and is arranged in a left-right staggered manner with the U-shaped bent portions superimposed on the tire equator L-L. Block 13 is 2 on the left and right
By arranging the pieces in a left-right staggered manner, the center block 12 and the side blocks 13 are tilted so that the bent part of the center block 12 is tilted in the tire rotation direction 15 and the side blocks 13 are tilted in the anti-tire rotation direction 15A. It is said to be an arranged herringbone block pattern. Further, the shoulder blocks 14 are short blocks 14 having a small length in the tire axial direction in the two left and right side blocks 13, and short blocks 14 having a large tire axial length in the left and right side blocks 13. As shown in FIG. 3, the kick surface portion 9 and the anti-kick surface portion 10 of the block 11 have a rising angle β, θ with respect to the outer surface of the tire. ing. In the illustrated embodiment, the angle α of the blocks forming the herringbone pattern is 90°<α125°. In other words, if α is 125° or more, as shown in Figs. 4 and 5, the traction force will be reduced because the road surface will not be scraped up and mud etc. will be swept away.
This is because if α is less than 90 degrees, mud, sand, and snow will be shoveled into the road surface too much, making it difficult to obtain a flotation effect, resulting in a sharp drop in running performance and traction performance (Figures 4 and 5). (see figure). Further, in the illustrated embodiment, in FIG. 3, the rising angle β of the kick surface portion 9 is 93° to 135°, and the rising angle θ of the opposite kicking surface portion 10 on the opposite side in the rotation direction is 90° to 135°.
It is said to be 130°. That is, β - θ = 3° ~ 20°, θ = 90 ~ 132°, β
= 93° to 135°, and by making a difference in the block cross-sectional inclination angles β and θ, it is possible to prevent mud, sand, or snow from forming on the road surface portion 9 on the block 11. , the snow becomes difficult to adsorb, and in the case of the anti-kick surface 10, the mud adsorbed to the block 11,
This promotes the removal of sand, snow, etc., and prevents mud, sand, etc. from adhering to the tire 1 and reducing the traction force. Furthermore, in FIG. 1, the side block 13 has a rhombus-shaped ground contact and a rear protrusion 13A in a part of the rhombus.
3A contributes to improving block rigidity. In addition, in FIG. 1, an earth removal section 16 is formed between the left and right ends of the block 8, and the lateral width L1 of this earth removal section 16 is less than or equal to the lateral width L12 of the front and rear blocks 8. As a result, even if the total number of blocks is reduced, the traction force by the blocks acts on substantially the entire block. Furthermore, the shoulder block 14 is designed to improve the traction edge effect by forming a slit 14A in the cross-sectional depth direction from the top surface thereof. Next, the tire according to the example of the present invention, the tire according to the comparative example, and the tire according to the comparative example were attached to the rear wheels of a three-wheel buggy and a four-wheel buggy, and the running performance on hard soil, mud, snow, and sand was evaluated. The evaluation of traction properties was as follows.

[Table] Other than Table 1 above, the shape, dimensions, etc. of the tire of the present invention are as follows. Tire size: Tubeless 24×9.00−11 Rim: 7.5×11 Tire outer diameter: 610mm Tire width: 238mm Number of circumferential pitches of block: 32 Ketled pattern section development width (W): 292mm In Figure 1,

【table】

[Table] Note that the tires of the comparative example are almost the same as the tires in the above table except for α, β, and θ. (Effects of the Invention) The present invention is as described above, and since the central blocks on the tire equator are shaped in a plan view and are arranged in a staggered manner from side to side, the force acting on the central blocks is distributed to the left and right. This allows for better straightness. In addition, the side blocks on the left and right sides of the center block are arranged in a staggered manner, with two on the left and one on the left, forming a herringbone-like block pattern with the center block, so the number of blocks is smaller than in the conventional example. As a result, it is possible to prevent mud clogging while ensuring turning performance, and this mud clogging can be prevented by providing an angular difference between the kick surface and the anti-kick surface of the block. improves. Furthermore, since the shoulder blocks have long and short lengths in the tire axial direction, even if the total number of blocks including the side blocks is reduced, the total traction force due to the blocks can be prevented from becoming small. It is possible to ensure running performance while reliably preventing clogging. Furthermore, the shoulder block contributes to improving the rigidity of the tire shoulder and suppresses excessive deformation, thereby improving turning performance.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a part of a tire tretz according to an embodiment of the present invention, and FIG. 2 is a sectional view of the same tire.
Fig. 3 is a cross-sectional view of the block, Fig. 4 is a graph of the relationship between the angle α and the running performance and traction index on hard soil (normal road surface), and Fig. 5 is also a graph of the relationship between the angle α on hard soil (normal road surface) and the traction index.
This is a relationship graph when the road surface is snowy. 1...Tire, 2...Tread, 3...Shoulder, 4...Side wall, 11...Block,
12...Central block, 13...Side block,
14...Shoulder block.

Claims (1)

[Claims] 1. An ultra-low pressure system in which a tread 2 located in the center is connected to both side walls 4 through a shoulder 3, and a large number of blocks 11 having a trapezoidal cross section are arranged on the tread 2 including the shoulder 3. In the pneumatic tire, the blocks 11 include a center block 12 arranged on the tire equator L-L, side blocks 13 arranged on both left and right outer sides of the center block 12, and side blocks 13 arranged on both left and right outer sides of the side blocks 13. The center block 12 is formed into a U-shape in plan view through a bent portion, and is arranged in a left-right staggered manner with the bent portion superimposed on the tire equator L-L. The side blocks 13 are arranged in a staggered manner, with two on the left and one on the left. The outer side block 13 is rotated in the anti-tire rotation direction 15A.
The shoulder block 14 has a herringbone pattern block pattern arranged in a perspective view, and furthermore, the shoulder block 14 has a short block 14 having a small length in the tire axial direction in the two left and right side blocks 13, and a short block 14 having a short length in the tire axial direction. In the partial block 13, the long block 14 has a large length in the tire axial direction, and the rising angle of each of the blocks 11 with respect to the outer surface of the tire is equal to the kick surface part 9.
An ultra-low pressure pneumatic tire characterized by having a large anti-kick surface part 10 and a small anti-kick surface part 10.